The present invention relates to a system for displaying color video as monochrome video on a color display, and more particularly to a system for automatically enabling and disabling a color killer circuit.
Contemporary color televisions incorporate control mechanisms for adjusting the chroma (intensity) and hue (shading) of the color television. Adjusting the chroma and the hue allows the video to be viewed in a manner suitable to a viewer's particular preferences. For example, some users prefer a bright image while other users prefer a dimmer image. A user typically adjusts the chroma and the hue merely once upon purchasing the television, and at most infrequently during the life of the television. Accordingly, the chroma and the hue are adjusted and remain unchanged regardless of whether the television is turned off, the power to the television is disconnected, or the television channel is changed. Moreover, after the chroma and the hue are properly adjusted, a user typically has no desire to modify them.
In recent years many video content providers have started to broadcast, or to otherwise provide for viewing, video such as classic movies originally filmed in black and white (monochrome), to which color has been artificially added. This process is generally known as colorizing. Although colorizing has been criticized as being somewhat artificial in appearance, many viewers enjoy watching colorized classic monochrome video.
However, to a significant number of viewers the colorization of classic monochrome video represents an intrusive alteration of the video's original content. By adjusting the chroma, the effects of the colorization of classic monochrome movies can be eliminated so that movies are displayed in monochrome. Thereafter, the user must readjust the chroma, preferably to its original setting, to view subsequent videos in color. Unfortunately, readjusting of the chroma is difficult if the user has forgotten the original chroma setting. In such a case, the user may adjust the chroma several times until a suitable image is achieved. Unfortunately, adjusting the chroma is time consuming, difficult, and frustrating if the original setting is forgotten.
Several known systems use a color killer circuit to eliminate color information and thereby convert color images to monochrome images. When the color killer circuit is enabled, colorized video is shown in black and white (monochrome). When the color killer circuit is disabled, colorized video is shown in color. Three patents that disclose such systems with color killer circuits are Engel, Reneau, and Ohara et al.
Engel U.S. Pat. No. 4,253,108 describes a color television receiver control system for enabling and disabling the limiting action of an automatic color limiter circuit. The color limiter circuit varies the threshold at which the color killer circuit inhibits reproduction of color images. Alteration of the operation of the automatic color limiter circuit and the color killer circuit may be effected manually or automatically. The color killer circuit is responsive to one of two conditions, namely, a relatively low amplitude input color signal or a relatively high amplitude input color signal. In either case, the system monitors the amplitude of the input color signal and enables the color killer circuit if the threshold happens to meet certain criteria. Such a system is unsuitable for the viewing of colorized videos in monochrome because the color killer circuit cannot be enabled regardless of the amplitude of the input color signal.
Reneau U.S. Pat. No. 4,298,884 describes a chroma amplifier that activates a color killer circuit based upon the received color signal strength. Like the Engel system, the Reneau system is unsuitable for the viewing of colorized movies in monochrome because the color killer circuit cannot be enabled regardless of the amplitude of the input color signal.
Ohara et al., U.S. Pat. No. 5,452,016 describe a color control circuit which sets a control line based on the relation of a received input color signal and a killer level. If the level of the input color signal fails to meet the killer level, then a coefficient controller controls a coefficient generated by a coefficient generator to perform a killer operation, thereby displaying the color video in monochrome. Like the systems discussed above, the Ohara et al. system is unsuitable for the viewing of colorized movies in monochrome because the color killer circuit cannot be enabled regardless of the amplitude of the input color signal.
Many televisions include on-screen programming to permit adjustments to the televisions settings. Some settings include, for example, a sleep timer, closed captioning, stereo, tone, alarm, clock, color, tint, brightness, sharpness, autocolor, and speakers. Such settings are adjusted and then the television operates as adjusted until the on-screen programming is reactivated to modify the settings. At least one television manufacturer markets a television with an on-screen programming monochrome/color option that displays the color video input signal in monochrome. Accordingly, when a user desires to view a video in monochrome, and in particular a colorized monochrome movie, the user activates the on-screen programming to activate the monochrome/color option for all channels. The television continues to display color in monochrome until the on-screen programming is reactivated and the monochrome/color option is deactivated so color video is displayed in color.
Unfortunately, many users of such a television may be unaware that a monochrome/color option exists under the on-screen programming feature that avoids the need to manually adjust the chroma. When the television is displaying images in monochrome, an unaware user may mistakenly believe that the television is broken. Attempting to repair a properly operating television, albeit displaying color video in monochrome, may entail adjusting the antenna, contacting the broadcast company, contacting the cable company, contacting the satellite content provider, adjusting the chroma and thereby disturbing its setting, adjusting the tuning, and in desperation striking the television in a desperate hope that the color will return. One potential solution is to place a sign on the television explaining the monochrome/color option, but this is burdensome and necessitates an undesirable sign obstructing the viewing area.
What is desired, therefore, is a television that does not burden unaware users with the potential misconception that when displaying monochrome video the television is not functioning properly. In addition, the television should permit automatic activation and deactivation of the color killer circuit.